1. Field of the Invention
This invention relates generally to a stairway construction and more particularly, to a novel stairway construction which consists of a plurality of elements which interconnect to form an articulating, self-supporting staircase.
2. Description of the Prior Art
It has been previously proposed to provide a stairway construction which consists of a plurality of stairway support elements, each element having a horizontal portion on which is mounted the stairway tread, and a vertical portion, which extends upwardly from the horizontal portion to interconnect with the element immediately above and which extends downwardly from the horizontal portion to interconnect with the element immediately below.
The most difficult problem encountered with these structures is to provide a self-supporting structure which is safe and secure. Each element must be secured to the adjacent element immediately above and immediately below in such a manner to ensure safety, yet such construction must be simple and easy to install on site with minimal time and tools being required. The structure must be designed to be economical yet aesthetically pleasing and must have the adaptability to be fully adjustable in height and in orientation. Space and size restrictions must be able to be accommodated for all possible installations.
The first attempt to provide such structures utilized a central column to which riser and tread members were attached. An example of such a structure is shown in U.S. Pat. No. 3,964,222 granted on June 22, 1976 to Geleijnse et al. Reference is also made to U.S. Pat. No. 3,916,591 granted on Nov. 4, 1975 to Agterhaf et al. which uses a spindle to which the steps are attached.
Free standing stairway constructions have also been attempted in the past. One such example is shown in U.S. Pat. No. 3,473,275 granted on Oct. 21, 1969 to Lappin which shows a stairway comprising a series of individual stair tread units, each connected by fasteners such as bolts or screws to each others. Other more recent constructions are shown in German Offenlegungsschrift No. 25 52 220 and German Offenlegungsschrift No. 2 129 753, U.S. Pat. Nos. 3,908,325; 4,285,178, and Canadian Pat. No. 1,005,964.
The principle concern of these patents and the inventions disclosed herein reside in the problem of securing the elements together in such a manner to provide a safe and secure structure which will not fatique over time. For example, Canadian Pat. No. 1,005,964 discloses a structure which uses telescopically interengageable metallic tubes as the vertical portions with bearing members to clamp the tubes together. Steel balls are used about the bearing members to increase the clamping effect.
Various forms of clamps and bolts have also been tried to prevent sagging of the structure over time. However, it has been found that all these structures will fatigue over time and fail to meet the building codes of many jurisdictions.